Molded plastic closures which can be threadably applied to associated containers for packaging products such as carbonated and non-carbonated beverages for example have met with widespread success in the marketplace.
Closures of this nature can be efficiently formed by compression molding and injection molding techniques, with the closures configured for tamper-evidence as may be required for some applications. These types of closures can provide highly effective sealing performance, even when used with containers having pressurized contents, with the threaded nature of the closures facilitating convenient removal, and re-application, by consumers.
In a manufacturing environment, it is desirable to be able to produce as many closures as possible in a given period of time, and for the closures to be applied to a suitable container. Therefore, in a typical molding process, a molded closure will be ejected from the molding apparatus before the closure has had time to completely cool. Particular regions of a closure can take longer to cool than others, especially if they comprise more material, and therefore have a greater mass in such regions. Such ‘hot spots’ can, by virtue of the fact that they take longer to cool, deform when the closure is ejected from the molding apparatus. Deformation as a result of this is particularly problematic in molding apparatus in which a fast cycle time is employed.
Generally speaking, it is desirable to reduce closure mass so that cooling is accelerated and raw material consumption is reduced and throughput increased.